Annealing effects on the microstructure and properties of an Fe-based Metallic-Intermetallic Laminate (MIL) composite

Abstract

430SS MIL composites were initially fabricated under semi-solid reaction at 655°C and then annealed at high temperature (1000°C) to obtain the ductile Fe-rich intermetallic phases. The microstructure evolution and micro-hardness distribution across the intermetallic/metal interfaces were investigated, as well as the experimentally and computationally evaluating the growth kinetics of the Fe-rich intermetallic layers. A multilayer structure (namely Al-rich layer, Fe-rich layer and B2 phase layer) with a complex mix of intermetallic phases (FeAl2, Cr5Al8 and FeAl) form in the high temperature annealed 430SS MIL composites. The FeAl phase with a B2 structure formed in the intermetallic layer provides a more gradual transition of mechanical properties across the intermetallic/metal layer. The growth mechanism of the Fe-rich layer is interface controlled, while the growth of the B2 phase layer is diffusion controlled based on both the experimental and numerical analysis. A relationship between the processing-microstructure-properties of the MIL composites has been established and applied to predict and tailor the microhardness distribution across the multi-layered structure of the 430SS MIL composites.